Revert "Represent git-submodule as nested projects"

This reverts commit 69998b0c6ff724bf620480140ccce648fec7d6a9.
Broke Android's non-gitmodule use case.

Conflicts:
	project.py
	subcmds/sync.py

Change-Id: I68ceeb63d8ee3b939f85a64736bdc81dfa352aed
5 files changed